Electrophysiological and mechanical interactions in the fetus are largely unstudied. There is an established need to enhance the current echocardiography/Doppler capabilities of recognizing the fetus at risk of life threatening cardiac complications. Direct simultaneous comparison of fetal magnetocardiography using Superconducting Quantum Interference Device (SQUID) magnetometry and Doppler will allow, for the first time, assessment of electromechanical disturbances associated with heart failure and severe arrhythmia. This instrument will directly address the fetal cardiac disorders that effect about 1-3% of all pregnancies. This proposal aims to develop an fMCG vector gradiometer instrument specifically designed for combined use with echocardiography for the characterization of the intrauterine clinical condition of fetuses with life- threatening arrhythmias, acquired heart failure, and structural congenital heart disease. The system will have in addition a very small tail and radial gap so the echo probe can be positioned very closely over the same area. Compared to existing conventional one-component magnetometers, the instrument will be inexpensive, lightweight and easily producible. The system can be either a stand-alone or an add-on to existing MEG rooms. Neither of the existing MEG or MCG systems are designed for these types of measurements. In addition the system will make the use of at least one type of Echocardiac transducer reliable when positioned 2 cm from the base of the system. This probe will be capable of being rigid adjacent to the system or adjustable in rotation and tilt remotely as desired. Several key technical issues were identified, which will be addressed in Phase II. Vector coils are needed to ensure that the (arbitrarily positioned) fetal heart can be detected with reasonable signal strength. There is a need to stabilize the transducer, while permitting the required degree of maneuverability for ultrasound imaging. Third is the need to reduce the size of the fMCG sensor array in order to provide greater access to the maternal surface for echo/Doppler imaging. Fourth is the development of optimal signal processing techniques for the new sensor configuration, particularly for reduction of non-stationary low frequency interference. And fifth is the need to better study the relationship between the echo/Doppler transducer positioning (angle and orientation) and the sensor array positioning, in order to facilitate the recording of additional or more traditional Doppler planes while not compromising, and perhaps even facilitating the quality of the fMCG signal. The findings on Phase I generated enough knowledge to develop, and assured the need of a suitable instrument capable of simultaneous ultrasound/fMCG recordings. The successful completion of this program has the potential to lead to a significant ability to identify fetal arrhythmias. In addition, this product should enhance assessment of fetal well-being by identifying risk factors for sudden fetal death, including cardiac ischemia, QT prolongation, and electromechanical dysfunction. This proposal aims to develop better methods of characterizing the intrauterine clinical condition of fetuses with life-threatening arrhythmias, acquired heart failure, and structural congenital heart disease by the development of an economical, noninvasive simultaneous fetal echocardiography and magnetocardiography system. Direct simultaneous comparison of fetal magnetocardiographic (fMCG) recordings in conjunction with Echocardiography and Doppler (echo/Doppler), will enhance current echo/Doppler capabilities of recognizing the fetus at risk of life-threatening cardiac complications. We are developing the first instrument specially designed for these dual measurements.